R-Theta 2-Axis Precision Motion Stages

February 24, 2022
R-Theta 2-Axis Precision Motion Stages for High Performance Motion Control

R-Theta stage motion systems are better suited to circular, elliptic and spiral motion patterns than conventional Cartesian 2-axis XY linear translation stages.

PI offers three classes of R-Theta stages.

  1. For the highest performance and precision, Air Bearing linear stages and air bearing rotary tables are used.
  2. Hybrid R-Theta systems use linear motor driven stages with mechanical bearings and direct-drive air bearing rotary tables.
  3. Direct Drive linear motor stages and direct drive rotary tables with mechanical bearings are also available.

R-Theta systems often find applications in precision laser / semiconductor applications due to higher throughput, higher precision and smaller footprint.

High Speed Motion Controllers

The stages are operated by PI’s ACS-based industrial motion controllers with ultra-fast triggers for synchronization with external equipment such as cameras, sensors or lasers. The fast controllers allow highly precise triggering with 0.01% time tolerance between signals. Trigger signals can be derived off absolute encoders or analog signals (sin/cos encoder), enabling higher precision, safer, and simplified solutions as compared to outdated digital encoder-only triggers. With the modern PI motion controllers, a trigger in an R-Theta configured system will work just as well as an XY position trigger, with the coordinate specifications simply defined in polar coordinates.

Related Glossary Terms

  • linear motor

    linear motor

    Functionally the same as a rotary motor in a machine tool, a linear motor can be thought of as a standard permanent-magnet, rotary-style motor slit axially to the center and then peeled back and laid flat. The major advantage of using a linear motor to drive the axis motion is that it eliminates the inefficiency and mechanical variance caused by the ballscrew assembly system used in most CNC machines.

  • tolerance


    Minimum and maximum amount a workpiece dimension is allowed to vary from a set standard and still be acceptable.